1. Technical Field
This invention relates to an image formation apparatus belt, a belt stretching unit and an image formation apparatus.
2. Related Art
For example, a color image formation apparatus adopting an intermediate transfer system using an intermediate transfer belt is available as an image formation apparatus using electrophotography. In the image formation apparatus, an intermediate transfer belt adapted to come in contact with a transfer section of an image supporter (for example, a photoconductive drum) on which a toner image is formed according to an electrophotographic process, etc., and rotate is stretched on a plurality of rolls. A plurality of toner images formed on the image supporter are primarily transferred so that they are once overlapped at the same position of the intermediate transfer belt and then the toner images transferred onto the intermediate transfer belt are secondarily transferred to a sheet of paper in batch. The multi-color toner image secondarily transferred onto the sheet is then fixed by a fixing unit and becomes a color image.
In addition, a color image formation apparatus of tandem type using a sheet conveying belt for conveying a sheet of paper so as to allow the sheet to pass through transfer sections of a plurality of image formation units is also available as an image formation apparatus including a belt. In the image formation apparatus, the image formation units each for forming a toner image of each color component individually are placed side by side and the sheet conveying belt is stretched on a plurality of rolls so as to come in contact with the transfer section of each image formation unit and rotate. The sheet attracted to the sheet conveying belt and held thereon is conveyed so as to allow the sheet to pass through the transfer sections of the image formation units, whereby the toner images formed in the image formation units are transferred to the same sheet of paper so that they are overlapped in order, and finally the image is fixed to form a color image.
In the image formation apparatus including the belt, highly accurate position control is indispensable for precisely overlapping the toner images. Hitherto, position control of a belt has been performed by detecting a specific position of the belt with a sensor.